Lights used in traffic and navigational control are generally point or near-point sources. Typically such sources are monochromatic, and the color designates a type of hazard in the vicinity of the light, or a particular traffic direction allowed, etc. For bidirectional or multidirectional indication, point sources may be arranged back-to-back or in an array, with differently colored sources used in each direction. Alternatively, a rotating source may be used. Examples include rotating airport beacons, and reversible traffic lane directional signals.